As a "ancient web developer": i will come back once you JS folks have agreed on a tool set and actually use it for more than 6 months.
It works as a joke too, but the vast majority of JS developers aren't using tools younger than 6 months old. Even current hotness Vue.js was originally released in 2015, and Webpack was initially released in 2012.
I haven't upgraded my projects to Webpack 2 yet. I'm interested but not compelled to, and I'll do it when it makes sense for me.
Does that make JavaScript a bad ecosystem? I have a hard time thinking of thoughtful major releases as a bad thing.
The churn in tooling is unavoidable even if you use slightly less fashionable frameworks.
I'm not claiming that all those transitions were for the best, far from it, but the real question for any language community to answer is: "how much churn is acceptable in the pursuit of better?" JS is an ongoing cultural experiment in seeing what happens when you turn that dial to 11.
And realistically speaking, yarn is not a discernable improvement over npm.
The cultural experiment has a huge cost to programmers and it's been an utter disaster. Even PHP has leapfrogged javascript.
Yarn will save you 10x the time you spend configuring it from using it just once. But go ahead, keep using NPM, new stuff is scary.
If there was a time when web folks agreed on a tool set I missed it.
It's not really about agreeing on everything, though, is it? What matters is having enough standardisation and longevity that you can make intelligent decisions today and expect your code to work for a useful length of time and to play nicely with code written by others who also make intelligent decisions today.
You can run a CGI process written in whatever programming language you want under any of the popular web servers today, and it will work essentially the same way as it did 20 years ago.
Until browser developers decided that backwards compatibility was too much trouble to continue supporting, which is a relatively recent development, you could also run Flash or Java applets written many years ago with essentially the same results today.